Hi When configuring the Arduino uno digital pins to work as i2c pins, are they automatically configured to use internal pull up pins? Thanks a lot. :slightly_smiling_face:

Thanks a lot :slightly_smiling_face:

[image] declas: When configuring the Arduino uno digital pins to work as i2c pins, are they automatically configured to use internal pull up pins? Internal pull-ups are only active when the IO lines are configured to work as input lines. In I2C, the SCL line is always output wrt Master, then…

[image] GolamMostafa: Internal pull-ups are only active when the IO lines are configured to work as input lines. Nope. You have to specify them in the pinMode function call, if you want them on or off. [image] GolamMostafa: In I2C, the SCL line is always output wrt Master, then how are w…

[image] Grumpy_Mike: They are also automatically set to have their pull up resistors enabled. By the "Wire" library code, not the chip itself.

Well I thought the preceding sentence [image] Grumpy_Mike: When using the I2C lines (both of them) they are set to a special type of output known as an open collector output. made it clear. However to make it ultra clear this setting of the pull up resistors is only done by the default wire…

[image] Grumpy_Mike: When using the I2C lines (both of them) they are set to a special type of output known as an open collector output. Open drain? [image] Grumpy_Mike: They are also automatically set to have their pull up resistors enabled. Does it mean that apart from Port-C's own …

[image] GolamMostafa: Open drain? Technically speaking correct, but it is well known that the use of open collector encompasses open drain as the topology of the circuit is the same. [image] GolamMostafa: Does it mean that apart from Port-C's own set of pull-up resistors, the I2C Logic a…

[image] Koepel: // activate internal pullups for twi. digitalWrite(SDA, 1); digitalWrite(SCL, 1); Whys are the above when the syntax is as follows:? [digitalWriteX]

[image] Grumpy_Mike: So if you want that disabled you have to specifically turn off the pullup resistors with a pinMode(A4, INPUT); pinMode(A5, INPUT); immediately after the Wire.begin(); call. Maybe better to use digitalWrite(SDA, 0); digitalWrite(SCL, 0); // or digitalWrite(SDA, LO…

Internal pull up resistor in i2c, Arduino uno

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Internal pull up resistor in i2c, Arduino uno

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